Slow magnetic relaxation behavior of a {Dy2} complex based on a large π-conjugated bridging ligand

Abstract

Binuclear lanthanide single molecule magnets (Ln-SMMs) based on large π-conjugated bridging ligands have shown potential in achieving excellent SMM performance. However, their members are still scarce until now. In this work, a novel binuclear Ln-SMM featuring a large π-conjugated bridging ligand, [Dy2(hfac)6(tpphz)]·CH2Cl2 (1), has been prepared. Its two DyIII centers are chelated and bridged by the large π-conjugated tetrapyrido[3,2-a:2′,3′-c:3′′,2′′-h:2′′′,3′′′-j]phenazine (tpphz) ligand. Three 1,1,1,5,5,5-hexafluoroacetylacetonate (hfac-) ions acting as terminal ligands further complete the square antiprism coordination geometry of each DyIII center. Magnetic measurements revealed that 1 exhibits zero field SMM behavior with a single magnetic relaxation process. The effective energy barrier (Ueff) is 13.79 K. Interestingly, dual relaxation behavior including well-separated slow relaxation (SR) and fast relaxation (FR) processes was further observed when a dc field was applied. It could be ascribed to the different single ion anisotropy of the DyIII centers, as well as a possible contribution of magnetic interactions in the system of 1. The Ueff values for the SR and FR processes are 27.3 and 1.30 K, respectively.